On Wed, Jul 2, 2025 at 7:31 AM <pan2...@intel.com> wrote:
>
> From: Pan Li <pan2...@intel.com>
>
> This patch would like to add the middle-end presentation for the
> unsigend saturation mul. Aka set the result of mul to the max
> when overflow.
>
> Take uint8_t as example, we will have:
>
> * SAT_MUL (1, 127) => 127.
> * SAT_MUL (2, 127) => 254.
> * SAT_MUL (3, 127) => 255.
> * SAT_MUL (255, 127) => 255.
>
> Given below example for uint16_t from uint128_t
>
> #define DEF_SAT_U_MUL_FMT_1(NT, WT) \
> NT __attribute__((noinline)) \
> sat_u_mul_##NT##_from_##WT##_fmt_1 (NT a, NT b) \
> { \
> WT x = (WT)a * (WT)b; \
> NT max = -1; \
> if (x > (WT)(max)) \
> return max; \
> else \
> return (NT)x; \
> }
>
> DEF_SAT_U_MUL_FMT_1(uint16_t, uint128_t)
>
> Before this patch:
> 15 │ <bb 2> [local count: 1073741824]:
> 16 │ _1 = (__int128 unsigned) a_4(D);
> 17 │ _2 = (__int128 unsigned) b_5(D);
> 18 │ _9 = (unsigned long) _1;
> 19 │ _10 = (unsigned long) _2;
> 20 │ x_6 = _9 w* _10;
> 21 │ _7 = MIN_EXPR <x_6, 255>;
> 22 │ _3 = (uint8_t) _7;
> 23 │ return _3;
>
> After this patch:
> 9 │ <bb 2> [local count: 1073741824]:
> 10 │ _3 = .SAT_MUL (a_4(D), b_5(D)); [tail call]
> 11 │ return _3;
>
> gcc/ChangeLog:
>
> * internal-fn.cc (commutative_binary_fn_p): Add new case
> for SAT_MUL.
> * internal-fn.def (SAT_MUL): Add new IFN_SAT_MUL.
> * optabs.def (OPTAB_NL): Remove fixed point limitation.
>
> Signed-off-by: Pan Li <pan2...@intel.com>
> ---
> gcc/internal-fn.cc | 1 +
> gcc/internal-fn.def | 1 +
> gcc/optabs.def | 2 +-
> 3 files changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/gcc/internal-fn.cc b/gcc/internal-fn.cc
> index 3f4ac937367..184f72132cc 100644
> --- a/gcc/internal-fn.cc
> +++ b/gcc/internal-fn.cc
> @@ -4423,6 +4423,7 @@ commutative_binary_fn_p (internal_fn fn)
> case IFN_ADD_OVERFLOW:
> case IFN_MUL_OVERFLOW:
> case IFN_SAT_ADD:
> + case IFN_SAT_MUL:
> case IFN_VEC_WIDEN_PLUS:
> case IFN_VEC_WIDEN_PLUS_LO:
> case IFN_VEC_WIDEN_PLUS_HI:
> diff --git a/gcc/internal-fn.def b/gcc/internal-fn.def
> index 8edfa3540f8..914ee9f278c 100644
> --- a/gcc/internal-fn.def
> +++ b/gcc/internal-fn.def
> @@ -282,6 +282,7 @@ DEF_INTERNAL_SIGNED_OPTAB_FN (MULHRS, ECF_CONST |
> ECF_NOTHROW, first,
>
> DEF_INTERNAL_SIGNED_OPTAB_FN (SAT_ADD, ECF_CONST, first, ssadd, usadd,
> binary)
> DEF_INTERNAL_SIGNED_OPTAB_FN (SAT_SUB, ECF_CONST, first, sssub, ussub,
> binary)
> +DEF_INTERNAL_SIGNED_OPTAB_FN (SAT_MUL, ECF_CONST, first, ssmul, usmul,
> binary)
Since you are using ssmul here as well please drop the fixed point
limitation on that optab as well.
OK with that change.
Richard.
>
> DEF_INTERNAL_SIGNED_OPTAB_FN (SAT_TRUNC, ECF_CONST, first, sstrunc, ustrunc,
> unary_convert)
>
> diff --git a/gcc/optabs.def b/gcc/optabs.def
> index 0c1435d4ecd..ea049378112 100644
> --- a/gcc/optabs.def
> +++ b/gcc/optabs.def
> @@ -135,7 +135,7 @@ OPTAB_NX(smul_optab, "mul$F$a3")
> OPTAB_VL(smulv_optab, "mulv$I$a3", MULT, "mul", '3', gen_intv_fp_libfunc)
> OPTAB_VX(smulv_optab, "mul$F$a3")
> OPTAB_NL(ssmul_optab, "ssmul$Q$a3", SS_MULT, "ssmul", '3',
> gen_signed_fixed_libfunc)
> -OPTAB_NL(usmul_optab, "usmul$Q$a3", US_MULT, "usmul", '3',
> gen_unsigned_fixed_libfunc)
> +OPTAB_NL(usmul_optab, "usmul$a3", US_MULT, "usmul", '3',
> gen_unsigned_fixed_libfunc)
> OPTAB_NL(sdiv_optab, "div$a3", DIV, "div", '3',
> gen_int_fp_signed_fixed_libfunc)
> OPTAB_VL(sdivv_optab, "divv$I$a3", DIV, "divv", '3', gen_int_libfunc)
> OPTAB_VX(sdivv_optab, "div$F$a3")
> --
> 2.43.0
>
